The first man to undergo a successful double arm transplant has spoken of his joy at the “indescribable feeling of being a whole man again".

German farmer Karl Merk made his first public appearance on Wednesday, almost three months after the ground-breaking 15-hour operation, and says he can already perform simple tasks such as opening doors and turning lights on and off.

"It was really overwhelming when I saw that I had arms again," the 54-year-old told reporters at a press conference at the Munich University Clinic.

Wearing support straps on his lower arms with a sleeveless black t-shirt that revealed exactly where his new arms had been grafted, an upbeat Merk added, "It’s just fantastic. These are my arms, and I'm not giving them away again.”

Merk lost his own arms in a corn shredder accident six years ago and admitted he was stunned at the success of the transplant in July, which required the skills of 40 staff, including surgeons, nurses and anesthesiologists.

"All in all, our wildest expectations have pretty much been fulfilled," said Christoph Hoehnke, one of the lead doctors helping Merk through his intensive in-patient program of physiotherapy and counseling. which is expected to last another four to six weeks.

Although there is still a risk that Merk’s immune system will reject the arms, his doctors say the current indications including nerve growth is good, though it may take up to two years before he relearns how to use his hands.

Merk says he is looking forward to eventually being able to feed and dress himself, “"and cruise around a little on my rollerblades".